Method and apparatus for input of coded image data

ABSTRACT

An image input device which includes a means for inputting image data, a memory for storing secret information and an operator for carrying out an operation by using the image data and the secret information.

RELATED APPLICATIONS

This is a divisional of application Ser. No. 12/572,357, filed Oct. 2,2009, which is a divisional of application Ser. No. 11/211,426, filedAug. 26, 2005, and now U.S. Pat. No. 7,603,561, which is a divisional ofapplication Ser. No. 08/777,246, filed Dec. 31, 1996, and now U.S. Pat.No. 7,000,112. It claims benefit of all three applications under 35U.S.C. §120, and claims benefit under 35 U.S.C. §119 of Japanese PatentApplication No. 003603/1996, filed Jan. 12, 1996; the entire disclosureof each of the four mentioned prior applications is hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an image input apparatus and to a method forpreventing forgery of image data.

2. Related Background Art

Image input systems which convert an image to digital image data shouldbe capable of providing high definition image at low cost. Accordingly,there has been developed image input apparatus which is capable ofproducing a high definition image with highly efficient coding.

Prior input apparatus which processed analog image signals were notsubject to easy forgery. However, recently developed digital image inputsystems which process images in digital form have been subject to easyforgery. As a result, the credibility of the output image data isweakened.

SUMMARY OF THE INVENTION

This invention is directed to overcoming the above described problem. Itis an object of the invention to provide an image input apparatus andmethod which can 30 ensure the integrity of digital image data. Thismethod and apparatus makes use of digital signature technology.

According to a publication of Eizi Okamoto of Kyouritu Syuppan, Inc., adigital signature assures that the person who purports to generate amessage or information is the true author of the message. This digitalsignature may be used by the recipient of the message as assurance thatthe information contained therein is true.

According to the invention, an image input apparatus generates aparticular digital signature in relation to image data; and outputs thisdigital signature together with the digital image data.

In an image receiving system, an entity which receives the digital imagedata and the digital signature will be able to ascertain theauthenticity of the image data by checking the relation between theimage data and the digital signature. And, if the relation between theimage data and the digital signature is inappropriate, the receivingentity will judge that the image data has been falsified or altered.Thus, the image input apparatus and the image receiving system guaranteethe authenticity of the image data and its credibility as evidence.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an embodiment of the invention;

FIG. 2 is a block diagram for a digital camera which serves as an imageinput apparatus;

FIG. 3 is a block diagram showing an embodiment of an image inputsystem;

FIG. 4 is a data format outputted by the image input system;

FIG. 5 is a block diagram of an image input system which outputs adigital signature; and

FIG. 6 is a data format outputted by the image input system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The First Embodiment

In the first embodiment of the invention, a public key cryptography isapplied to an image input apparatus as an algorithm of a digitalsignature. The apparatus uses a secret key corresponding to the publickey as its own secret information.

It should be understood that this embodiment is only one example.Another embodiment may be realized by using another algorithm instead ofthe public key cryptography, provided that the other algorithm is ableto verify original information which is being based upon the originalinformation and the secret information.

First, a public key cryptography will be described. Then an image unitwill be described as well as a detailed process for a digital signature.Finally, the process for verifying the digital signature will bedescribed.

(Public-Key Encryption System)

Public-key cryptography is one type of cryptography. Public-keycryptography uses two different keys, namely, an encryption key and adecryption key. In public key cryptography, the encryption key ispublished, but the decryption key is not published.

Public-key cryptography provides a certification function which assuresto the receiver that transformed information has not been changed andthat the sender is not a pretender. Generally, public-key cryptographyhas been considered as one of the most effective methods for protectingdata.

The operation for encrypting an original message (M) by using a publickey (PK) is: E (PK, M). The operation for decrypting the encryptedmessage (M) by using a secret key (SK) must satisfy the following twoconditions:

(1) The operation for encryption E(PK, M) must be easily carried outusing the public key PK and the operation for decryption D(SK, M) mustbe easily carried out using the secret key SK by a person who knows thesecret key SK; and

(2) Even if the user has both the public key PK and the process oroperation for encrypting E (PK, M), it must be nearly impossible toobtain the original message M without the secret key SK in view of theextremely large number of operations that would have to be carried outfor determining the original message M.

A secret communication will be able to be realized by satisfying theabove conditions (1) and (2) and the following condition (3):

(3) The operation for encrypting all original message M with the publickey PK must be possible; and the operation for decryption D(SK, E(PK,M)) must produce a recognizable message (M);i.e. D(SK,E(PK,M))=M.

This means that anyone will be able to encrypt the message (M) by usingthe public key PK; but only a person who knows the secret key SK will beable to decrypt the encrypted message.

On the other hand, certification will be realized by satisfyingconditions (1) and (2) and the following condition (4):

(4) The operation for decrypting a message (M) with the secret key SK ispossible; and the operation for encrypting E (PK, D (SK, M).)=M must bepossible.

This means that only a person who knows the secret key SK will be ableto decrypt the message (M) by using the secret key SK. So, if someonewho has a different secret key SK, and pretends to be a person who knowsthe secret key SK, tries to decrypt the message (M) by using that secretkey SK, he will not be able to obtain the message (M);i.e. E(PK,D(SK′,M))≠M.

The receiver will therefore find out the forgery carried out by somethird party.

On the other hand, if D(SK, M) is altered by someone, for example, toD(KS, M)′, he will not be able to obtain the message (M);i.e. E(PK,D(SK,M)′)≠M.

Therefore, in this case also, the receiver will find out themodification carried out by the illicit act of a third party.

The result of the operation for decrypting D(SK, M) is referred to as:“A Digital Signature for Text M”.

The typical public key cryptography is as follows.

Cryptography which can realize both secret communications andauthenticated communications is known as:

“RSA cryptography”—(R. L. Rivest, A. Shamir and L. Adleman: “A Method ofObtaining Digital Signatures and Public-key Cryptosystems”, Comm. of ACM1987);

“R cryptography”—(M. Rabin: “Digitalized Signatures and Public-keyCryptosystems”, MIT/LCSTR

35 212, Technical Report MIT. 19797);

“W cryptography”—(H. C. Williams: “A Modification of the RSA Public-keyEncryption Procedure”, IEEE Trans. Inf. Theory, IT-26, 6, 1980); and

“MI cryptography”—(T. Matsumoto and H. Imai: “A Class of AsymmetricCryptosystems Based on Polynomials Over Finite Rings”, IEEEInternational Symp. on Information Theory, 1983), etc.

Cryptography which can realize secret but authenticated communicationsis known as:

“MH cryptography”—(R. C. Merkle and M. E. Hellman: “Hiding Informationand Signatures in Trapdoor Knapsacks”, IEEE Trans. Inf. Theory, IT-24,5, 1987; “GS cryptography”—(A. Shamir and R. E. Zippel: “On the Securityof the Merkle-Hellman Cryptographic Scheme”, IEEE Transs. Inf. Theory,IT726, 3, 1980);

“CR cryptography”—(B. Chor and R. L. Rivest: “A

Knapsack Type Public-key Cryptosystem Based on Arithmetic InfiniteField”, Proc. Crypto 84);

“M cryptography”—(R. J. McElice: “A Public-key

Cryptosystem Based on Algebraic Coding Theory”, DSN Progress Rpt., JetPropulsion Lab., 1978);

“E cryptography”—(T. E. El Gamel: “A Public-key cryptocsystem andSignature Scheme Based on Discrete Logarithms”, Proc. Crypto84, 1984));

“T cryptography”—(Sigeo Tsuzii: “A Public-key System Based on MatrixAnalysis” [Japanese], IT85-12, 1985, etc.

Cryptography which is able to realize authenticated communications butsecret communications is known as:

“S cryptography”—(A. Shamir: “A FastSignature Scheme”, ReportMIT/LCS/TM-107, MIT Laboratory for Computer Science, Cambridge, Mass.,1978);

“L cryptography”—(K. Liberherr: “Uniform Complexity and DigitalSignature”, Lecture Note in Computer Science 115 Automata, Language andProgramming, Eighth Colloquium Acre, Israel, 1981):

“GMY cryptography”—(S. Goldwasser, S. Micali and A. Yano: “StrongSignature Schemes”, ACM Symp. on Theory of Computing, 1983);

“GMR cryptography”—(S. Goldwasser, S. Micali and R. L. Rivest: “AParadoxical Solution to the Signature Problem”, ACM Symp. on Foundationof Computer Science, 1984);

“OSS cryptography”—(H. Ong, C. P. Schnorr and A. Shamir: “An EfficientSignature Scheme Based on Quadratic Equations”, ACM Symp. on Theory ofComputing 1984);

“OS cryptography”—(T. Okamoto and A. Shiraisi: “A Fast Signature SchemeBased on Quadratic Inequalities”, IEEESymp. on Theory of Computing,1984), 15 etc.

(Construction of the Image Input Device)

An embodiment of the invention to which digital signature based on thepublic-key cryptography is applied will be described herein below withreference to FIG. 1. In FIG. 1, an image input device, such as a digitalcamera, is shown by functional blocks. A line which connects the blocksrepresents a control and data bus.

The image input device includes an image pick up part 1 which convertsan optical image into an electrical signal. The image pick-up part 1includes a signal processor, an analog-to-digital converter, an imageprocessor and a coder. The electrical signal is processed in theprocessor, converter and coder and is output as a digital signal.

The image input device also includes: a controller 2 (CPU) forcontrolling the image input device by performing predeterminedoperations based on control software stored in a memory; a memory 3 forstoring the control software; a work memory 4 for use during operationof the apparatus; an operation switch 5 for inputting commands anddesignating an area of an image for the digital signature of a user; amechanical portion. 6 for controlling mechanical operations of the imageinput device based on commands from the controller 2; and a main memory7 for storing the processed image output. The mechanical portion 6, forexample, includes motor and an optical system, composed of a lens and ashutter. In addition, the image input device also includes: an ‘externalinterface 8 for connecting the input device with other external devices,for example a personal computer, a memory device, etc., for transferringimage data or control software to such external devices; and a generator9 for generating a digital signature for the inputted image data basedupon a predetermined algorithm.

The above described image input device operates to obtain image data inthe following manner. A user initiates an input command by operating theoperation switch 5. This causes the controller 2 to respond to thecommand and control software to control the image portion 1 and themechanical portion 6. Thereafter, image data is supplied to thegenerator 9; and the generator 9 produces a digital signature whichcorresponds to an area-of the image represented by the image data. Theimage data and digital signature are recorded and/or sent to theexternal device via the interface 8, according to a command.

Alternatively, the image data is first stored in the memory 3; andthereafter only a part of the image data, 35 which corresponds to onearea of the image recorded in the memory, is read out and is fed to thegenerator 9.

The generator 9 generates the digital signature based on this image datafor this area.

One embodiment, which is used as a camera for producing digital imagesand can produce a digital signature based on a public-key cryptography,has a secret key SKcam. In this embodiment, the secret key SKcam, and analgorithm for generating the digital signature Dcam, are stored in thegenerator 9. In addition, a public key PKcam and an algorithm forverifying an Ecam are known by the entity who wishes to check theintegrity of the information. The procedure for generating the digitalsignature is described below.

(Digital Signature Generation)

Image data (I) is generated by the image pick-up part 1 and is fed tothe generator 9. The generator 9 carries out an operation by using thesecret key (SKcam) and an algorithm for generating a digital signature;and outputs the digital signature (Dcam (SKcam, I)). The image data (I)and the digital signature (Dcam (SKcam, I)) are recorded in the memory 7and/or are output to an external device via the interface 8.

The detailed procedure for verifying that the image data −(I) and thedigital signature corresponding to the image data (I) are actuallygenerated by the same image input device is described below. In thisembodiment, an image input system consists of the image input device andverifying means.

(Digital Signature Verification)

The image data (I′) and the digital signature (D′cam (SKcam, I)) areverified by carrying out the following operation using a public key(PKcam) and the algorithm for verifying the digital data (Ecam);i.e. I′=Ecam(PKcam,D′cam(SKcam,I)).

If the above equation produces a recognizable image, the image data (I′)is the image data (I) which was input from the image pick-up part. Onthe other hand, if the above equation does not produce a recognizableimage, the image data (I′) is not the image data (I). Accordingly, theverifier can determine whether the image data (I′) was modified orforged.

According to this embodiment, the digital signature is generated basedon the same area of the image designated by the user. Therefore, thetime for generating the digital signature can be shortened; and the loadrequirements of the system can be reduced.

The Second Embodiment

The second embodiment, which uses a public key cryptography as analgorithm for digital signature and a secret key which is stored in theexternal device, is described herein in reference to FIG. 1. In thisembodiment, the external device which stores the secret keys ofregistered users (SKinan) (corresponding to each registered user'spublic key (PKman)) and an algorithm for generating a digital signature(Dman) (corresponding to an algorithm for verifying the digitalsignature), is a portable device. This device is a data processingdevice; and it is connected to the image input device via the interface8. On the other hand, the public key (PKman), and the algorithm forverifying the digital signature, are known by the entity who also wishesto check the integrity of the input image data.

The basic operation for inputting image data is described as follows.When inputting (for example, V⁻ photographing), information, theexternal device is connected to the input device via the interface 8.The user inputs a command for photographing by operating the switch 5and a command for generating the digital signature by inputting his ownuser's number (which is similar to an identification number). Thecontroller then ascertains the user's number and controls the imagepick-up part 1 and the mechanical part 6 based on the control softwarestored in the memory 3. The image data is then fed to the generator 9.If the user's number is correct, i.e. if it coincides with one of theregistered numbers, the controller 2 communicates with the externaldevice via the interface 8 and gets the secret key (SKman) of the userand the algorithm for generating the user's digital signature. Thecontroller 2 then carries out an operation using the user's secret key(SKman) and the algorithm to generate the user's digital signature. Thedigital signature and the image data are recorded and/or output to theexternal device according to command. In the above described embodiment,the detailed procedure for generating the digital signature is asfollows:

(Digital Signature Generation)

The controller 2 ascertains the user's number and downloads the secretkey (SKman) and the algorithm for generating the digital signature fromthe external device, via the interface 8; and enters them into thememory 4. The image data generated by the image pick

up part 1 is fed to the generator 9. The generator 9 carries out anoperation by using the secret key (SKman) and the algorithm forgenerating a digital signature; and it outputs the digital signature(Dman (SKman, I)). The image data (I) and the digital signature (Dman(SKman, I)) are recorded in the memory 7 and/or are output to theexternal device via the interface 8.

The detailed procedure for verifying that the image data (I) and thecorresponding digital signature have actually been generated by theabove input image device when the external device is connected with theinput image device, is as follows:

(Digital Signature Verification)

Image data (I)′ to be examined and the digital signature (D′man (SKman,I)) to be examined are verified by carrying out an operation which usesa public key (PKman) for verifying the digital data (Ecam).i.e. I′=Eman(PKmanDman(SKman,I)).

If the equation produces a recognizable image, the image data (I′) isthe image data that was input by the image input device. On the otherhand, if the equation does not produce a recognizable image, the imagedata I′ is known to be not the true image data (I); and that theexamined image data (I′) has been modified by a different person at adifferent place. Consequently, the user can determine that the examinedimage data (I′) is modified or forged data. Accordingly, an image inputsystem which guarantees that the image has been input by the externaldevice is realized in this embodiment.

In this embodiment, the users' numbers are changed or another user'snumber is additionally registered by a person who is authorized tochange or add to the user numbers. Therefore, impersonation can beabsolutely prevented.

Third Embodiment

The third embodiment, which uses a public key cryptography as thealgorithm for a digital signature, and in which a secret key is storedin an external device which can operate on the data, is describedhereinbelow, also with reference to FIG. 1.

(Digital Signature Generation)

The controller 2 transfers the image data, which was generated by theimage pick-up part 1, to the external device via the interface 8. Thegenerator 9 in the external device caries out an operation by using theuser's secret key (SKman) and the image data based on the algorithm forgenerating a digital signature. The external device then outputs thedigital signature (Dman (SKman, I)) and the image data and transfersthem to the image input device via the interface 8. In the image inputdevice, the transferred image data (I) and the digital signature (Dman(SKman, I)) are recorded in the memory 7 and/or outputted to theexternal device via the interface 8.

The detailed procedure for verifying that the image data (I) and thedigital signature corresponding to the image data (I) have actually beengenerated by the above image input device when the external device isconnected with the image input device, will now be described.

(Digital Signature Verification)

Verification in the third embodiment is the same as in the secondembodiment.

The Fourth Embodiment

The fourth embodiment, which uses a public key cryptography as analgorithm for digital signature. In this embodiment, respective secretkeys are stored in both the external device and in the image inputdevice, will now be described, again with reference to FIG. 1.

(Digital Signal Generation)

The controller 2 downloads the secret key (SKman) and the algorithm forgenerating the digital signature (Dman) into the memory 4 and into thecontroller 2, from the external device via the interface 8. The imagedata (I) which was generated by the image pick-up part 1 is fed into thegenerator 9 in the image input device. The generator 9 caries out anoperation by using the secret key SKman and the digital signature (Dman(SKman, I)) based on the algorithm for generating the digital signature(Dman); and outputs the digital signature of the camera Dcam(SKcam,Dman(SKman, I)). The image data (I) and the digital signature of thecamera Dcam(SKcam, Dman(SKman, I)) are recorded in the memory 7 and/oroutputted to an external device via the interface 8.

The detailed procedure for verifying that the image data (I) and thedigital signature corresponding to theimage data (I) have actually beengenerated by the particular external device when that external device isconnected with the image input device, will now be described.

(Digital Signature Verification)

The received image data (I′) and the received digital signature D′cam(SKcam, Dman (SKman, I)) are verified by carrying out the followingoperation using the public key PKcam and the algorithm for verifying thedigital data Ecam, the algorithm for verifying the digital data Eman andthe public key PKman; i.e.I′=Eman(PKman,Ecam(PKcam,D′cam(SKcam,Dman(SKman,I)).

If the operation produces a recognizable signature, this shows that theexamined image data (I′) is the true image data (I) which was input fromthe image input device. On the other hand, if the operation is not good,the examined image data (I′) is seen to be not the true image data (I);and that it has been modified by another person or at another location.The user can thus determine that the examined image data (I)′ has beenmodified or forged. Therefore, this embodiment provides an image inputsystem which guarantees that the correct image is input from theexternal device. It will be seen that the reverse order of generatingthe digital signature, by the image input device and the external deviceand verifying the digital signature, will provide the same result. Also,the algorithm for generating the digital signature in the externaldevice may be stored in the image input device.

The Fifth Embodiment

In this embodiment, the image input device generates the digitalsignature by using compressed image data. The compressed data transformis represented herein as “C”; and the entity who wishes to verify thatthe image data is correct knows the compressed data transform “C”. Theimage input device in this embodiment is the same as in the abovedescribed embodiments.

(Digital Signature Generation)

The controller 2 carries out its operation using compressed image datafor generating the digital signature rather than the image data which isinput by the image input part 1. The other procedures involved in thegeneration of the digital image signature are the same as in the aboveembodiments. For example, the image data and the digital signatureD′cam(SKcam, c(I)) is verified by using the algorithm for verifying the,digital signature Ecam and the pubic key PKcam; i.e. the verificationconforms to the following equation:C(I′)=.Ecam(PKcam,D′cam(SKcam,C(I).

If the above equation holds, the examined image data (I′) is seen to bethe image data that had been input by the image input device. On theother hand, if the equation does not hold, the examined image data (I′)is seen to be different from the original image data (I). In this mannerthe verifier can confirm that the image data (I′) is modified or forgedinformation.

The Sixth Embodiment

In this embodiment, the image input device is a digital camera; and apublic key algorithm is used as the cryptography for generating andverifying the digital signature. In addition, both the digital cameraand the external device have their own secret key for use with thepublic key encrypted information. This embodiment is described hereinbelow with reference to FIG. 2.

(The Construction of the Digital Camera)

In FIG. 2, each block represents a functional portion of the digitalcamera; and each line which connects the blocks represents a control ordata bus. The digital camera has an image input portion 10 (IMG) whichconverts an optical image into an electrical signal, a signal processor11 (PRC) which includes an analog-to-digital converter, and an imageprocessor, a coder and a converter which processes the electrical signaland outputs a digital signal. The digital camera also includes: acontroller 12 (CPU) for performing predetermined operations based on acontrol program; a memory 13 (ROM) for storing the control program; awork memory (i.e. a DRAM) 14 which is used as a work area; an operationswitch 15 (OP-SW) for inputting commands by the user; a microphone 16(MIC) for the input of audio information; a main memory 17 (STRG) forstoring the output (i.e. image and audio data and/or informationregarding a situation or condition for photographing) of the image inputportion 10 and/or the microphone 16, etc.

In addition, the digital camera has: an external interface 18 (I/F) forconnecting the camera with an external device (for example, a personalcomputer, a memory device, etc.) and for communicating the image dataand/or control software with the other external device; a generator 19(CODEC) for generating a digital signature for the image data and/oraudio data based on a predetermined algorithm; an interface 20 for aPCMCIA card based on PCMCIA standards. Also, the digital camera has aliquid crystal display (LCD) display 21 and a light emitting diode (LED)type lamp 22.

The basic operation for generating image data with this digital camerawill now be described. The external device is connected with theinterface 18; and the user inputs commands by operation of the switch15. The controller 12 communicates with the external device, and thecontroller 12 controls the image input portion 10 and processes acompressed image data, etc. by using the secret key, the algorithm forgenerating the digital signature stored in the external device and thesecret key, and the algorithm for generating the digital signaturestored in the digital camera.

The image data and the digital signature are recorded and/or sent to theexternal device via the interface 18 or the PCMCIA interface 20, basedon command. Alternatively, the image data is first stored in the memory3, and thereafter the data is read out from the memory 3 and fed intothe generator 9. The generator 9 generates the digital signature basedon this data.

An embodiment comprising a camera as above described may be used for thegeneration of a digital signature based on public-key cryptography. Thecamera described in this embodiment has a secret key. The secret key ofthe camera is expressed as SKcam. The algorithm of the camera forgenerating the digital signature is expressed as Dcam; the algorithm forverifying the digital signature is expressed as Ecam; the public key isexpressed as PKcam; and the algorithm for data compression is expressedas H. Also in this embodiment, the secret key stored in the externaldevice is expressed as SKman; the algorithm for generating the digitalsignature is expressed as Dman; the algorithm for verifying the digitalsignal is expressed as Eman; and the public key is expressed as PKman.

Further, in this embodiment, the algorithm for verifying the digitalsignature Ecam and the public key PKcam of the digital camera, thealgorithm for verifying the digital signature Eman and the public keyPKman of the external device and an algorithm for compressing the dataH, are known by the entity who wishes to verify to correctness of thedata.

The procedure for generating the digital signature will be describedhereinbelow.

(Digital Signature Generation)

The image data (I) generated by the image input part 11 is fed to thegenerator 19. The generator 19 caries out an operation by using thesecret key SKcam and the algorithm for generating the digital signatureDcam; and outputs the digital signature Dcam (SKcam, H(I)) to theexternal device via the interface 18. The external device caries out anoperation by using the secret key SKman and the algorithm for generatingthe digital signature Dman and the digital signature Dcam (SKcam, h(I))and returns the digital signature Dman (SKman, Dcam(SKcam, h(I))) to thedigital camera via the interface 18. The image data (I) and the digitalsignature Dman (SKman, Dcam(SKcam, h(I) are recorded in the memory 17and/or are output to the external device via the interface 18.

The detailed procedure for verifying that the image data (I) and thedigital signature corresponding to the image data (I) were actuallygenerated by the above image input device is as follows.

(Digital Signature Verification)

The image data (I) and the digital signature Dcam(SKman, Dcam(SKcam,H(I)) are verified by carrying out an operation which uses the publickey PKman, the algorithm for verifying the digital data Eman of theexternal device, the public key PKcam, the algorithm for verifying thedigital data Ecam, and the compression algorithm H of the digitalcamera.

For example,H(I′)=Ecam(PKcam,D′man(SKman,Dcam(SKcam,H(I′)))).

If the equation holds, the image data (I′) is the true image daa thathad been input by the digital camera.

On the other hand, if this equation does not hold, the image data (I′)will be understood not to be the true image data (I). Accordingly, theverifier can determine that the image data has been modified or forged.

Another Embodiment

This invention includes all image input devices and systems obtained bycombining each of the above described embodiments.

FIG. 3 shows, in conceptual form, the construction of the image inputsystem with a verification function. In FIG. 3, an image input device30, similar to the image input devices of the above embodiments, isconnected with a portable external device 31 via an external interface32. Also, a checking device 33 is connected with another external device34 to verify the digital signature.

For example, the checking device may be a personal computer which has analgorithm for verifying the digital signature Ecam, the public key PKcamof the image input device, the algorithm for verifying the digitalsignature Eman, and the public key PKman of the external device.Alternatively, the checking device may be a personal computer connectedto the external device; and the external device may have an algorithmfor verifying the digital signature Ecam, the public key PKcam of theimage input device, the algorithm for verifying the digital signatureEman, and the public key PKman of the external device.

The term “image” in FIG. 3 refers to an object being photographed; and“(I)” refers to image data. An image input device which is connectedwith the external device 34 via the interface serves as the checkingdevice. The image data is fed selectively into the generator (C-CODEC)30 a and into the external device 32 via the interface; and/or is outputfrom the generator 30 a to the interface 32.

As shown in FIG. 3, an adder or mixer 35 is provided for adding ormixing the output from the generator 30 a or the external device 31 toor and the image data (I).

The output of the adder 35 is illustrated in FIG. 4. The image data andthe digital signature corresponding to the image data (I) are packagedin a predetermined unit as shown in FIG. 4.

It will be appreciated that if the image input system uses the RSAcryptosystem, the input system output will be only the digitalsignature. This is because the image data can be recovered from thedigital signature in the RSA cryptosystem. Accordingly, even if theinput system does not have the CODEC system for data compression, thesystem can record and/or communicate only the digital signature withoutreducing the memory capacity and the communication efficiency.

The system and the form of its output are shown in FIGS. 5 and 6,respectively. The image input device of this invention need not be onlya digital camera. It may, for example, be a scanner, a copying machine,a facsimile, a filing system, an optical character recognition (OCR)system, etc. Also, this invention is not limited to image data but itmay be used for the processing of several other kinds of information.

According to the above described embodiments, the operator cannotgenerate the digital signature without the image input device or theexternal device which has the secret key and the algorithm forgenerating the digital signature. Accordingly anyone can easily verifythe correctness of the signature by using the public key and thealgorithm for verifying the digital signature corresponding to thesecret key and the algorithm for generating the digital signature,respectively.

Thus, according to the above described embodiment, the image inputdevice or the image input method can guarantee that the image data hadbeen generated by the image input device or system without modificationor forgery; and it can guarantee the authenticity of the digitalinformation as well as the image data, the audio data, etc., asevidence. Thus, this embodiment can be used to protect from themalicious use of digital information.

What is claimed is:
 1. An image input apparatus comprising: an imagedata generating unit that generates image data; an interface unit that(a) transmits the image data to an external device and receivesverification information from the external device, wherein the externaldevice receives image data from the image input apparatus, converts theimage data received from the image input apparatus into compressed imagedata, generates, using a secret key included in the external device andthe compressed image data, the verification information, and transmitsthe verification information to the image input apparatus, and whereinthe verification information is used to verify whether the image data isaltered or not; and a memory that stores the image data and theverification information.
 2. The image input apparatus according toclaim 1, wherein the verification information corresponds to a digitalsignature.
 3. The image input apparatus according to claim 1, whereinthe secret key included in the external device corresponds to a secretkey used in public key cryptography.
 4. The image input apparatusaccording to claim 1, wherein the image input apparatus includes adigital camera.
 5. The image input apparatus according to claim 1,wherein the image input apparatus includes one of a scanner, a copyingmachine, and a facsimile.
 6. The image input apparatus according toclaim 1, wherein the interface unit transmits the image data and theverification information to the external device.
 7. A method comprising:transmitting, to an external device, image data generated in an imageinput apparatus; receiving verification information from the externaldevice, wherein the external device receives image data from the imageinput apparatus, converts the image data received from the image inputapparatus into compressed image data, generates, using a secret keyincluded in the external device and the compressed image data, theverification information, and transmits the verification information tothe image input apparatus, and wherein the verification information isused to verify whether the image data is altered or not; and storing theimage data and the verification information in a memory included in theinput apparatus.
 8. The method according to claim 7, wherein theverification information corresponds to a digital signature.
 9. Themethod according to claim 7, wherein the secret key included in theexternal device corresponds to a secret key used in public keycryptography.
 10. The method according to claim 7, wherein the imageinput apparatus includes a digital camera.
 11. The method according toclaim 7, wherein the image input apparatus includes one of a scanner, acopying machine, and a facsimile.
 12. The method according to claim 7,further comprising transmitting the image data and the verificationinformation to the external device.
 13. An image input apparatuscomprising: an image data generating means for generating image data; aninterface means for transmitting the image data to an external deviceand receiving verification information from the external device, whereinthe external device receives image data from the image input apparatus,converts the image data received from the image input apparatus intocompressed image data, generates, using a secret key included in theexternal device and the compressed image data, the verificationinformation, and transmits the verification information to the imageinput apparatus, and wherein the verification information is used toverify whether the image data is altered or not; and a storing means forstoring the image data and the verification information.
 14. The imageinput apparatus according to claim 13, wherein the verificationinformation corresponds to a digital signature.
 15. The image inputapparatus according to claim 13, wherein the secret key included in theexternal device corresponds to a secret key used in public keycryptography.
 16. The image input apparatus according to claim 13,wherein the image input apparatus includes a digital camera.
 17. Theimage input apparatus according to claim 13, wherein the image inputapparatus includes one of a scanner, a copying machine, and a facsimile.18. The image input apparatus according to claim 13, wherein theinterface means transmits the image data and the verificationinformation to the external device.
 19. A method comprising: receiving,from an image input apparatus, image data generated in the image inputapparatus; converting the image data received from the image inputapparatus into compressed image data; generating, using a secret keyincluded in an external device and the compressed image data,verification information which is used to verify whether the image datais altered or not, wherein the external device is capable of connectingto the image input apparatus; and transmitting the verificationinformation to the image input apparatus, wherein the image inputapparatus includes an interface unit that transmits the image data toexternal device and receives the verification information from theexternal device, and a memory that stores the image data and theverification information.
 20. The method according to claim 19, whereinthe verification information corresponds to a digital signature.
 21. Themethod according to claim 19, wherein the secret key included in theexternal device corresponds to a secret key used in public keycryptography.
 22. The method according to claim 19, wherein the imageinput apparatus includes a digital camera.
 23. The method according toclaim 19, wherein the image input apparatus includes one of a scanner, acopying machine, and a facsimile.
 24. The method according to claim 19,further comprising receiving the image data and the verificationinformation from the image input apparatus after the verificationinformation is transmitted from the external device to the image inputapparatus.
 25. An external device which is capable of connecting to animage input apparatus, the external device comprising: a receiving unitthat receives, from the image input apparatus, image data generated inthe image input apparatus; a converting unit that converts the imagedata received from the image input apparatus into compressed image data;a generating unit that generates, using a secret key included in theexternal device and the compressed image data, verification informationwhich is used to verify whether the image data is altered or not; and atransmitting unit that transmits the verification information to theimage input apparatus, wherein the image input apparatus includes aninterface unit that transmits the image data to the external device andreceives the verification information from the external device, and amemory that stores the image data and the verification information. 26.The external device according to claim 25, wherein the verificationinformation corresponds to a digital signature.
 27. The external deviceaccording to claim 25, wherein the secret key included in the externaldevice corresponds to a secret key used in public key cryptography. 28.The external device according to claim 25, wherein the image inputapparatus includes a digital camera.
 29. The external device accordingto claim 25, wherein the image input apparatus includes one of ascanner, a copying machine, and a facsimile.
 30. The external deviceaccording to claim 25, wherein the external device receives the imagedata and the verification information from the image input apparatusafter the external device transmits the verification information to theimage input apparatus.